The German laid-open application DE 43 35 965 A1 describes a combined motor starter with a power switch on the mains side and a series-connected contactor on the load side as well as an electronic unit for measurement, control and monitoring. The two switching devices have mechanical contact systems, and the electronic unit has electronic releases for the motor protection and the short-circuit protection. Due to the electronic releases of the electronic unit, conventional releases, such as bimetallic relays and quick-action releases, can be replaced and elaborate designs for facilitating a short-circuit current release can be avoided. In addition, the electronic overload monitoring allows for wide adjustment and release ranges of the electronic releases.
A three-phase electronic motor starter is described in the German laid-open application DE 10 2013 111 954 A1. The motor starter is realized by means of a contactor with mechanical contacts and a plug-on module with semiconductor switches. The module is used to reduce the very high load of the mechanical switching contacts of the contactor due to the high starting currents occurring particularly, when an electric motor is started. For that purpose, the semiconductor switches of the plug-on module are connected parallel to the switching contacts during the activation and deactivation process of the contactor by means of a corresponding control such that the switching contacts can switch almost without power, thus being subjected to a reduced load. The plug-on module can have an integrated motor protection circuit breaker that has release electronics and one current transformer per phase. On the basis of the output signals of the current transformers, the release electronics control a deactivation of the power supply to the motor and particularly effect a deactivation of the motor power supply in case of excessive currents.
From the German laid-open application DE 10 2009 012 942 A1, a motor starter designed for the use as a ventilator control device is known which has semiconductor switches for switching phases of a three-phase main power supply of the motor windings and a microcontroller as an electronic control unit for the semiconductor switches. In addition, there are transducers present for two of the three phases of the three-phase main power supply, the current measurement signals of which are fed to the microcontroller which, on the basis of the signals, controls the main switches, thus being able to implement a motor protection function.
The German laid-open application DE 197 42 916 A1 teaches a control for electric motors that are integrated particularly in movable and/or hand-operated machines, such as blenders, electric drills, grinders, etc. The control has a semiconductor switch as the main switch and has an overload protection function for the motor, which is based on a measurement of the current consumption of the motor. In addition, specific operating conditions of the motor can be adjusted by means of a potentiometer and a push-button field.
From the German laid-open application DE 100 03 692 A1, a semiconductor-based motor starter with reverse function is known.